The U.S. Supreme Court decision upholding the Obama administration's health care law opens the door for millions more to get coverage through the expansion of Medicaid, the public health insurance for the poor. But if history is any guide, college students could feel the pinch as states cut aid to higher education to expand health care.

Why? Now Medicaid is split between states and the federal government. And although the federal government will pay the entire cost of the expansion beginning in 2014, three years later states will have to begin sharing the cost. That might leave less money than ever for higher education. The result: higher tuition and fees as academic institutions scramble for ever-scarcer dollars from state budgets.

Tuition for the University of California already has tripled in a dozen years. State funding for the UC and CSU systems has dropped to 1998-99 levels. The community college system, at least, is guaranteed a minimum level of taxpayer funding through Proposition 98. But the state's once-proud tradition of generously funding its public colleges and universities has slipped beneath a rising tide of medical bills.

Researchers have long noted the correlation between the rising cost of Medicaid and falling state support for public colleges. Medicaid is "the biggest challenge casting a shadow on public higher education's future," according to a 2004 Brookings Institution study by Peter Orszag and Thomas J. Kane. States have an incentive to expand Medicaid, the study said; they are rewarded with more federal dollars for doing so. But they have no similar incentive to increase aid to colleges and universities. Lower tuition costs often result in residents getting less money in federal financial aid or tax credits.

Until two decades ago, the largest and second-largest budget priorities in most states were elementary and secondary education and state colleges and universities. But in 1990, Medicaid elbowed aside support for higher education in most state budgets. The recession of the 1990s increased Medicaid rolls as people lost their employer-provided health care. Funding for higher education diminished. When the recession ended, higher education didn't make up for lost ground.

This recession has been especially severe, and the result is equally dramatic. Nationwide, state governments now spend a higher percentage of their budgets on Medicaid than anything else, according to the National Association of State Budget Officers.

California's cost has gone up, too. The state has allocated nearly $15 billion for Medi-Cal, the state version of Medicaid, in fiscal year 2011-12, a 50 percent rise in 10 years. "Clearly, Medi-Cal is a cost driver in this state," said H.D. Palmer, spokesman for the California Department of Finance.

Once the Affordable Care Act - a.k.a. Obamacare - begins in 2014, more than 7 million Californians will become newly eligible for coverage. Yet Diana Dooley, head of the California Health and Human Services Agency, is an optimist that costs can be controlled. "I think we can save money," she insisted. "The potential is there. We won't save in an absolute way. We can mitigate the rate of increase."

A look at the state budget reveals another fiscal pressure that takes money away from public colleges: the cost of prisons.

The cost of prisons has more than doubled in California in 10 years, from $4.8 billion to $9.8 billion in 2011-12. The good news is that soaring cost is driving prison reform - and increasing the search for ways to reduce the inmate population. But medical costs are complicated and challenging to lower.

So where does this leave California's public universities and colleges? A report released in March, "Public Higher Education in California: Examining the Financial Landscape of the 21st Century," has a provocative answer. Written by three Stanford University graduate students for the nonprofit organization California Competes, it argues that the higher education system in California is on its way to becoming essentially private through lack of state funding.

California's per-student funding, the report says, has dropped 68 percent since the 1990-91 school year. If trends continue, funds for the UC system will run out by 2022, and the California State University system will be at only 25 percent of its most recent peak.

"The more realistic view is that higher education will be chronically underfunded," said Robert Jackman, one of the report's authors.

"Medi-Cal won't take the brunt of cuts. Higher education will," said David Hoffert, another author. "Colleges and universities will get the scraps."

A harsh assessment, perhaps. But one thing is certain: It isn't about to get any easier.

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